1. Field of the Invention
The present invention relates to a vehicle control system, which performs a vehicle control operation in conformity with a road state.
2. Description of Related Art
In a navigation system, an absolute position of a vehicle is sensed based on both of absolute positioning data and relative positioning data. The absolute positioning data is obtained by satellite navigation, which uses a GPS sensor. The relative positioning data is obtained by dead-reckoning navigation, which uses, for example, a gyrosensor and a vehicle speed sensor. A current position of the vehicle is displayed on a road map, which is indicated by map data. When an error exists in the road map, which is indicated by the map data, relative to the actual road, the absolute position of the vehicle does not coincide with the road map, which is indicated by the map data. Therefore, in the navigation apparatus, the position of the vehicle is corrected to coincide with the road map, which is indicated by the map data. That is, a map-matching operation is performed to obtain the position of the vehicle on the basis of the road map, which is indicated by the map data. As described above, in the navigation apparatus, the position of the vehicle is adjusted and is displayed to coincide with the road map. Thus, even in an area where the road map, which is indicated by the map data, differs significantly from the actual road, the position of the vehicle can be displayed in conformity with the road.
In recent years, it has been proposed to perform a vehicle control operation according to a road state through use of the navigation apparatus. For example, Japanese Unexamined Patent Publication JP-A-2005-59839 (corresponding to US 2005/0027419 A1) teaches a system, which adjusts optical axes of headlights of the vehicle according to a road state (a road extending direction on a vehicle front side), which is determined based on a road map that is indicated by map data. In such a system that adjusts the optical axes of the headlights according to the road state determined based on the road map, which is indicated by the map data, the optical axes of the headlights may be controlled in a manner that is not consistent with the actual road state in an area (e.g., a mountain road) of a relatively low accuracy where the accuracy of the road map, which is indicated by the map data, is relatively low. Therefore, in the system recited in Japanese Unexamined Patent Publication JP-A-2005-59839, the optical axis of only one of the left and right headlights is adjusted according to the road state that is determined based on the road map, which is indicated by the map data.
In the system recited in Japanese Unexamined Patent Publication JP-A-2005-59839, which adjusts the optical axis of only one of the left and right headlights according to the road state that is determined based on the road map, which is indicated by the map data, the level of the deterioration in the optical axis control operation in the above-described area of the relatively low accuracy can be reduced to a half level. However, the advantages of the optical axis control operation may be disadvantageously reduced to a half level in an area of a relatively high accuracy in the road map, which is indicated by the map data.